1. Field of the Invention
The present invention relates to a clock spring connector applied to an automobile steering system or the like and using a flexible cable for electrical connection between a fixed member and a movable member, and particularly to an alignment mechanism for aligning the fixed member and the movable member with a neutral position.
2. Description of the Related Art
A clock spring connector includes a flexible cable used for connecting a fixed member and a movable member rotatably mounted on the fixed member, and is used as an electrical connection device of an automobile steering system or the like.
In a generally known clock spring connector of this type, a flat cable comprising a plurality of conductor wires, which are laminated with two insulating films, is loosely spirally contained in a cable holding space interposed between the fixed member and the movable member, one end of the flat cable being fixed to an outer cylindrical portion formed in one of the fixed member and the movable member, and the other end being fixed to an inner cylindrical portion formed in the other member.
When the movable member is rotated, the clock spring connector permits the flat cable contained in the cable holding space to be wound on the side of the inner cylindrical portion or rewound on the side of the outer cylindrical portion in accordance with the rotation direction of the movable member. It is thus possible to constantly hold electrical connection between the fixed member and the movable member relatively rotated, with acting substantially no tension on the flat cable within the range from the state where the flat cable is completely wound on the side of the inner cylindrical portion and the state where the flat cable is completely rewound on the side of the outer cylindrical portion.
When the clock spring connector configured as described above is incorporated into a steering system, the clock spring connector must be incorporated so that the movable member at a neutral position of a steering wheel can be rotated for the same angle in the normal and reverse directions. An alignment mechanism has been thus proposed in which an indicator gear is axially supported by the fixed member, and a projection which can engage with the gear is provided on the movable member so that the movable member and the fixed member are aligned by rotating the gear for a predetermined angle when the movable member is rotated for 360.degree. . However, this conventional alignment mechanism has the problem that the need for disposing the gear on the outside of the outer cylindrical portion of the fixed member increases the outer diameter of the clock spring connector.
The above conventional clock spring connector employs a difference between the diameters of the outer cylindrical portion and the inner cylindrical portion for winding and rewinding the flat cable. When the rotation angle of the movable member is constant, the length of the flat cable can thus be decreased as the difference between the diameters is increased. However, since the diameter of the inner cylindrical portion is unconditionally determined by the diameter of a rotational shaft, for example, the automobile steering shaft, on which the clock spring connector is provided and since the difference between the diameters of the outer cylindrical portion and the inner cylindrical portion cannot be much increased because of the demand for decreasing the size of the system, the difference between the diameters of the outer cylindrical portion and of the inner cylindrical portion cannot be much increased. The clock spring connector generally thus requires a long flat cable which causes difficulties in the production thereof, thereby causing the problem that the total cost of the clock spring connector is increased.